The present invention relates generally to an automatic tension control device for regulating the tension in a filamentary material being withdrawn from a spool. More particularly, the present invention relates to a magnetic spool drive which retains a spool of filamentary material rotatably mounted on a spindle in non-slipping engagement with a magnetic chuck secured to a brake drum. More specifically, the present invention relates to such a magnetic spool drive wherein the magnetic chuck includes a mechanism for positive mechanical engagement of the spool flange to restrain relative slippage during spool rotation.
Filamentary materials including fibers in single and multiple strands are produced in long lengths and conveniently wound on spools for various uses. The filamentary materials may be natural or synthetic fibers, glass or metal. Such filamentary materials are commonly used as reinforcement for plastic or elastomeric compounds or may themselves be fabricated into integral items as is done in the textile industry. Regardless of the application, it is customary to withdraw the filamentary material from the spool at or near the location it is being used. To facilitate such removal, the spool is customarily mounted on a tension control device or tension controller having a spindle which permits the spool to rotate as the filament is withdrawn under controlled tension. In many industrial applications, a plurality of filamentary materials are simultaneously incorporated into the product such that a number of tension control devices are mounted in an array or creel configuration in close proximity to each other.
In steel-belted radial tire building applications metal spools are employed which carry large quantities of steel filament such that a loaded spool is cumbersome and sufficiently heavy to be difficult to manually load onto the spindles of tension control devices mounted at various heights off the ground in a typical creel arrangement. As a result, powered creel loaders with spool grasping devices have been developed to assist in loading spools onto the spindles of an array of tension control devices. Nonetheless, problems have been encountered in properly positioning a spool on the spindle of a tension controller and maintain the spool properly positioned relative to a spool drive mechanism, particularly during operations where the tension in the filament is high or where extreme fluctuations may occur in the payout speed at which filament is withdrawn from a spool.
It has long been known in the industry to employ a drive pin mounted on the brake drum at a position located a distance from the spindle which engages a hole in the flange of the spool to thereby physically preclude the spool from rotating relative to the brake drum. In some instances, spool drives employing these drive pins have been known to create substantial noise on large creel arrangements due to the moving interengagement between the pin and the bore in the spool flange. Another disadvantage of the drive pin spool drive is that during rotation of the spool and spindle, the spool may move away from the drum and thereby disengage the drive pin, particularly in installations where the spindle is essentially horizontally mounted such that gravity does not assist in maintaining the spool engaged with the drive pin. A most significant disadvantage of the drive pin spool drive is the difficulty which an operator experiences when loading a spool of wire filament on a spindle because it is necessary to perfectly aligning the drive pin with the hole in the spool flange and assuring that it is fully inserted to be operational. In creels, which may have 40-50 or more tensions controllers, significant production time can be lost in properly mounting spools on each of the tension controllers.
A more recently developed spool drive employed a cylindrical magnet on a brake drum mounted within a generally cylindrical metal cup. The magnetic coupling provided for ease of mounting the spool on the spindle as absolutely no rotational alignment was necessary to align a drive pin with a hole in the spool flange or the like. However, with only magnetic coupling between the spool drive and the spool, undesirable relative rotation between the spool and the spool drive attached to the brake drum may take place under certain operating conditions.
A variation of the original magnetic drive employs a magnetized toothed ring which meshes with the raised radial ribs in the flange of the metal spools. The teeth engaging the flange between the ribs are said to provide a greater surface for magnetic attraction between the magnetized ring and the spool flange. This design, however, is subject to rotational disengagement between the spool and the spool drive during acceleration attendant starts and stops for filament payout. This takes place because the teeth, upon slight rotational slippage, ride up on the ribs so the teeth are disengaged from the area between the ribs so that the ring engages only the top of the ribs and the magnet is displaced axially therefrom. This reduces the magnetic attraction of the spool, thereby effecting rotational disengagement allowing slipping between the spool and the magnetic ring. In this disengaged condition, however, the magnetic force may be insufficient to re-engage the teeth of the ring with the flange of the spool between the ribs, thereby leaving the spool disengaged. This is particularly true in installations wherein the spindle is horizontal or substantially horizontal, rather than inclined, so that there is no gravity assistance in reseating the spool on the toothed ring.
It is an object of the present invention is to provide a tension controller for filamentary material which employs a magnetic spool drive to maintain a magnetic plastic or metallic spool of the filamentary material in engagement with the spool drive. Another object of the invention is to provide such a tension controller wherein the magnetic spool drive restrains the spool from both rotational and axial disengagement from the spool drive even during the acceleration attendant starting and stopping the payout of the filamentary material. A further object of the invention is to provide such a tension controller which employs a spool drive having a mechanical restraint in combination with a magnet to further restrain relative rotation or slippage between a spool and the spool drive.
Another object of the present invention is to provide a tension controller for filamentary material which employs a magnetic spool drive which is adaptable for operation despite manufacturing variations in various metal spools by a manufacturer and even variations in spools among different spool manufacturers. A further object of the invention is to provide such magnetic spool drive which has a positive flange engagement mechanism employing a plunger which engages the flange of a spool and particularly the raised rib thereon to restrain relative rotation between the spool drive and a spool. Yet another object of the invention is to provide such a magnetic spool drive having a flange engagement mechanism with a spring loaded plunger that provides resistance to rotational slippage by the plunger engaging a rib on a spool flange while permitting limited slippage under extreme rotational loading conditions by temporary retraction of the plunger yet allowing the spool to remain within the magnetic influence of the magnet. Another object of the invention is to provide such a magnetic spool drive wherein the magnetic spool drive couples a positive flange engagement mechanism with a tubular sleeve housing a magnet that engages a central contact area that may be recessed in the flange of a spool, thereby maintaining the spool in the area of magnetic influence of the magnet of the spool drive.
A further object of the present invention is to provide a tension controller which has a magnetic spool drive having a mechanical restraint to preclude relative rotation between a spool and the spool drive that permits random positioning of the spool relative to the spool drive during spool loading. Still another object of the invention is to provide such a tension controller that achieves consistent operation during all operating conditions with a minimum of operator supervision or intervention. Yet another object of the invention is to provide a magnetic spool drive for a tension controller that is of rugged construction, that can be easily repaired, and that can be retrofitted on existing tension controllers.
In general, the present invention contemplates a spool drive for selectively retaining a spool having end flanges with radial ribs and a central contact area about a bore while filamentary material on the spool is payed out under tension including, a spindle adapted to receive the bore in the spool, a magnetic chuck surrounding and rotatable with the spindle, and a positive flange engagement mechanism associated with the magnetic chuck biased into contact with an end flange of the spool and adapted to engage the radial ribs to restrain rotational slippage between the magnetic chuck and the spool.